Page 443 - IJB-9-3

International Journal of Bioprinting Gelatin-PVA crosslinked genipin bioinks for skin tissue engineering

4. Discussion indicated that most of the bioinks were printed at the lower
printing temperatures, and 23 C was selected as the most
o
Tissue engineering using 3D bioprinting technology help optimum printing temperature for the extrusion-based
constructs biological structures that highly mimic native bioprinting . In addition, low printing temperatures are
[40]
tissue. It is an authentic bioconvergence strategy before required to extrude low-viscosity bioinks to allow consistent
the establishment in future personalized or precision deposition of bioinks. In this study, the viscosity of the
medicine applications. One of the main advantages of 3D GPVA bioinks increased with the addition of PVA and
bioprinting is the ability to include various bioinks or cell crosslinker (GNP). This finding was similar to that in a
mixtures into specific spatial orientations or layers in the previous study by Yang et al., which showed that the addition
printed hydrogels . In addition, this printing technology of PVA significantly affects the viscosity of gelatin hydrogels,
[33]
will enable live cells to react appropriately to the 3D-printed that is, the viscosity of the gelatin solution increased as the
[34]
designs . The revolutionary idea behind this biomatrix is concentration of PVA increased . Therefore, the addition
[41]
to employ it as a one-time post-implantation cellular skin of PVA and GNP into the bioinks was able to support the
replacement. The hydrogels will progressively degrade on printability of the bioinks at room temperature.
the injury site, followed by the regeneration of new tissue. Next, the physical properties were used to evaluate
Briefly, the encapsulation of cells in the bioinks with a layer- the performance of the desired hydrogel. Developing a
by-layer bioprinting concept is thought to encourage cell
proliferation, accelerating the healing process. Therefore, this biodegradable hydrogel for wound healing application is
highly desired to allow it to be degraded at an appropriate
study aimed to use extrusion-based bioprinting technology timeline following new tissue regeneration. Since rapid
to develop a functional cellular skin replacement that fits wound closure is necessary to prevent infection, the
the intended wound shapes and sizes using the formulated
bioinks composed of natural (GE) and synthetic-based designated hydrogels must not be degraded for at least
polymers (PVA) crosslinked with GNP, a natural crosslinker. 14 days before wound healing applications in the in vivo
model . A study by Zandi et al. suggested that in vivo
[42]
4.1. Physical properties of hybrid bioinks models could achieve 90% wound closure after treatment
[43]
with bioscaffolds for 2 weeks . The GPVA hydrogels
A printable biomaterial should have great printing resolution possessed an acceptable biodegradation rate for future
and excellent shape fidelity for irregular wound shape and wound healing applications. For comparison, crosslinked
facilitate surgeon handling. Brittle and soft hydrogel will gelatin hydrogels with the addition of PVA enable prolonged
limit surgical handling . Moreover, the consistent flow of
[35]
bioinks, which allows repeatable deposition of bioinks is a durability as compared to GE_GNP hydrogel only. This
finding was similar with a previous study by Hezaveh &
key feature of printed biomaterials . In general, multiple Muhamad, which indicated that utilizing genipin in the
[36]
deposition layers of bioinks will influence the geometrical hydrogels can prevent it from bursting in order to control
accuracy and structural integrity. As more layers are stacked, its durability . Thus, raising the concentration of PVA
[44]
the shape accuracy decreases as compared to a single layer
of hydrogel. A previous investigation by De Stefano et al. on and crosslinker will slow down the biodegradation rate
of the hydrogels at the injury site. In addition, a previous
the multiple layers of bioinks depositions yielded the results study by Mahnama et al. has proven that gelatin hydrogels
similar to our findings, in which the shape fidelity of the incorporated with PVA in higher ratio have the slowest
multilayer hydrogels was significantly reduced by 6 layers [45]
of square printed grids compared to the single layer . As biodegradation rate after 27 days .
[37]
a result, the printed filaments tended to collapse and merge Besides, in wound healing application, one of the
between each other. Besides, a printable bioinks should have characteristics that contributed to the skin’s barrier
an optimum printing temperature and viscosity to preserve function is surface wettability. The hydrophilic properties
cell viability for extrusion-based bioprinting technique. of the hydrogels were confirmed through contact angle
Basically, the optimization of the printing temperature is analysis, which showed that all printed GPVA hydrogels
depending on the viscosity of the hydrogels. Since the sol- possessed hydrophilic properties that may be caused
gel temperature for gelatin-PVA is low, our study revealed by the hydrophilic nature of gelatin and PVA polymer.
the same findings as in previous studies by Chimene et al. However, the incorporation of PVA into gelatin hydrogels
and Shie et al., in which they recommended that excellent reduced the hydrophilicity of the printed hydrogels. This
structural fidelity could be achieved by printing the intended finding was similar with a previous study by Cheng et al.,
bioinks at room temperature (23 ± 2°C) as compared to 25 which indicated that the hydrophilicity of the gelatin-PVA
[46]
± 2°C and 19 ± 2°C [38,39] . Moreover, our findings also can hydrogels was relatively lower than gelatin hydrogels .
be supported by a previous study by Ding & Chang, which Hydrophilicity of bioinks is a crucial characteristic that

Volume 9 Issue 3 (2023) 435 https://doi.org/10.18063/ijb.677